Background and aims: Inflammatory bowel disease (IBD) develops from a combination of genetic and environmental factors. The aim of this study was to determine the contribution of established environmental risk factors and genetic risk on age of IBD diagnosis in a diverse cohort.
Methods: IBD patients in clinic completed detailed questionnaires. Blood was drawn for genetic analysis. Environmental risk factors and age of diagnosis were analyzed by ethnicity (Hispanic/Latinx or non-Hispanic White [NHW] individuals) and IBD subtype (ulcerative colitis or Crohn's disease [CD]). Weighted genetic risk scores and environmental risk scores were developed. We examined the relationship between environmental risk scores, genetic risk scores, and age of diagnosis.
Results: A total of 2952 patients were included: 58.9% had CD. A total of 46.83% were of Hispanic background. Early life exposures like cesarean delivery and being born in a developed country were associated with a younger age of IBD diagnosis. Childhood exposures such as frequent plastic water bottle use and having more than 1 bathroom at home were associated with a younger age of IBD. Hispanic and NHW individuals shared similar susceptibilities to environmental exposures. Environmental factors explained 21% of the variance in age of CD diagnosis and 39% in ulcerative colitis. In models incorporating genetic risk score and environmental risk score, the environment was the only significant factor associated with younger age of IBD diagnosis in all groups.
Conclusions: Early life and childhood exposures impact IBD diagnosis and influence Hispanic and NHW individuals similarly. A cumulative environmental risk score contributes more to age of IBD diagnosis than genetic risk.
Keywords: Crohn’s Disease; Environment; Genetics; Hispanic/Latinx; Inflammatory Bowel Disease; Ulcerative Colitis.
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